This is the most expensive penny in the Universe. It's now on Mars, after an exciting $2.5 billion ride. Previously, the most expensive Lincoln penny in history was a 1943 copper-alloy cent that was sold for $1.7 million in a 1996 auction. That's peanuts compared to the cost of putting this coin up there, however.

In fact, if you take into account the total weight of Curiosity, the total cost of the penny is not that high: its 2.5 grams would only cost about $7,000. But being the first and only penny on Mars-and any other place outside Earth, as far as I know-I'm sure it would fetch a lot more than $1.7 million at any auction.

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The penny is part of the Mars Hand Lens Imager (MAHLI) camera's calibration target. The calibration target is attached to a shoulder joint of the arm that holds the camera, and contains red, green and blue color chips, different white point chips, a "metric standardized bar graphic and a stair-step pattern for depth calibration."

The penny sits between the last two. Usually, Earth geologists use a penny to know the scale in their photographs. But why include it when you already have an accurate metric scale there? According to MAHLI Principal Investigator Ken Edgett-at Malin Space Science Systems, San Diego-it's "a tip of the hat to geologists' informal practice of placing a coin or other object of known scale in their photographs."

It was Edgett himself who bought this very special penny with his own money, just to put it on the rover. It is a 1909 "VDB" cent, "from the first year Lincoln pennies were minted, the centennial of Abraham Lincoln's birth, with the VDB initials of the coin's designer-Victor David Brenner-on the reverse."

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That's the kind of commitment that NASA engineers put in their projects.

And here is a picture of MAHLI taken on Curiosity's 30th day (SOL 30)—right on the surface of Mars. It was taken after scientists at the Jet Propulsion Laboratory ordered the robotic arm to raise to the height of the rover's head. The MastCam then took the shot and sent it to Earth. It looks extremely cool and crisp. This is the kind of quality everyone was expecting.

According to NASA, you can see that there's "a thin film or coating of Martian dust on" its lens, "accumulated during Curiosity's final descent to the Martian surface, as the Mars Science Laboratory spacecraft's descent stage (or sky crane) engines were disrupting the surface nearby."

The reddish circle near the center of the Mastcam Sol 30 image is the window of MAHLI's dust cover, with a diameter a little less than a soda can's diameter. Inside the lens, each of the nine glass lens elements and the front sapphire window are bonded or cemented in place by a red-colored silicone RTV (room temperature vulcanizing) material. This is a space-qualified "glue" that holds the lens elements in place. When the MAHLI is viewed from certain angles, this material gives one the impression that the inside of the lens is red.

On the right of the image you can see Curiosity's dust removal tool, which is a motorized wire brush, according to NASA. The dust removal, however, is not for cleaning the lenses of any camera on the rover. The designers—Honeybee Electronics of New York—say it's made "to expose the natural surfaces of Martian rocks obscured by layers of dust deposited by aeolian processes." That's sciencespeak for clean marian rocks.